Suppression of electrical interference in an ignition system is the more effective the smaller the rate of increase of current and the smaller the peak current value. It has been proposed to use as the material for the distributor electrodes a lanthanum chromite ceramic whose resistivity is in the range of between 0.1 and 100,000 ohm-centimeters (see Japanese Patent Publication 52-156 240 of Dec. 26, 1977).